3 #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
4 #define CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
6 #include <cds/intrusive/details/michael_set_base.h>
7 #include <cds/details/allocator.h>
9 namespace cds { namespace intrusive {
11 /// Michael's hash set, \ref cds_urcu_desc "RCU" specialization
12 /** @ingroup cds_intrusive_map
13 \anchor cds_intrusive_MichaelHashSet_rcu
16 - [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"
18 Michael's hash table algorithm is based on lock-free ordered list and it is very simple.
19 The main structure is an array \p T of size \p M. Each element in \p T is basically a pointer
20 to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded.
21 However, each bucket may contain unbounded number of items.
23 Template parameters are:
24 - \p RCU - one of \ref cds_urcu_gc "RCU type"
25 - \p OrderedList - ordered list implementation used as bucket for hash set, for example, MichaelList, LazyList.
26 The intrusive ordered list implementation specifies the type \p T stored in the hash-set, the reclamation
27 schema \p GC used by hash-set, the comparison functor for the type \p T and other features specific for
29 - \p Traits - type traits, default is \p michael_set::traits.
30 Instead of defining \p Traits struct you can use option-based syntax with \p michael_set::make_traits metafunction.
33 Before including <tt><cds/intrusive/michael_set_rcu.h></tt> you should include appropriate RCU header file,
34 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
35 For example, for \ref cds_urcu_general_buffered_gc "general-purpose buffered RCU" you should include:
37 #include <cds/urcu/general_buffered.h>
38 #include <cds/intrusive/michael_list_rcu.h>
39 #include <cds/intrusive/michael_set_rcu.h>
42 // Hash functor for struct Foo
44 size_t operator()( Foo const& foo ) const { return ... }
47 // Now, you can declare Michael's list for type Foo and default traits:
48 typedef cds::intrusive::MichaelList<cds::urcu::gc< general_buffered<> >, Foo > rcu_michael_list;
50 // Declare Michael's set with MichaelList as bucket type
51 typedef cds::intrusive::MichaelSet<
52 cds::urcu::gc< general_buffered<> >,
54 cds::intrusive::michael_set::make_traits<
55 cds::opt::::hash< foo_hash >
59 // Declares hash set for 1000000 items with load factor 2
60 rcu_michael_set theSet( 1000000, 2 );
62 // Now you can use theSet object in many threads without any synchronization.
68 #ifdef CDS_DOXYGEN_INVOKED
69 class Traits = michael_set::traits
74 class MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >
77 typedef cds::urcu::gc< RCU > gc; ///< RCU schema
78 typedef OrderedList bucket_type; ///< type of ordered list used as a bucket implementation
79 typedef Traits traits; ///< Set traits
81 typedef typename bucket_type::value_type value_type ; ///< type of value stored in the list
82 typedef typename bucket_type::key_comparator key_comparator ; ///< key comparing functor
83 typedef typename bucket_type::disposer disposer ; ///< Node disposer functor
85 /// Hash functor for \ref value_type and all its derivatives that you use
86 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
87 typedef typename traits::item_counter item_counter; ///< Item counter type
89 /// Bucket table allocator
90 typedef cds::details::Allocator< bucket_type, typename traits::allocator > bucket_table_allocator;
92 typedef typename bucket_type::rcu_lock rcu_lock; ///< RCU scoped lock
93 typedef typename bucket_type::exempt_ptr exempt_ptr; ///< pointer to extracted node
94 typedef typename bucket_type::raw_ptr raw_ptr; ///< Return type of \p get() member function and its derivatives
95 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
96 static CDS_CONSTEXPR const bool c_bExtractLockExternal = bucket_type::c_bExtractLockExternal;
99 typedef cds::intrusive::michael_set::implementation_tag implementation_tag;
103 item_counter m_ItemCounter; ///< Item counter
104 hash m_HashFunctor; ///< Hash functor
105 bucket_type * m_Buckets; ///< bucket table
109 const size_t m_nHashBitmask;
114 /// Calculates hash value of \p key
115 template <typename Q>
116 size_t hash_value( Q const& key ) const
118 return m_HashFunctor( key ) & m_nHashBitmask;
121 /// Returns the bucket (ordered list) for \p key
122 template <typename Q>
123 bucket_type& bucket( Q const& key )
125 return m_Buckets[ hash_value( key ) ];
127 template <typename Q>
128 bucket_type const& bucket( Q const& key ) const
130 return m_Buckets[ hash_value( key ) ];
137 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
138 - it has no post-increment operator
139 - it iterates items in unordered fashion
141 typedef michael_set::details::iterator< bucket_type, false > iterator;
143 /// Const forward iterator
145 For iterator's features and requirements see \ref iterator
147 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
149 /// Returns a forward iterator addressing the first element in a set
151 For empty set \code begin() == end() \endcode
155 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
158 /// Returns an iterator that addresses the location succeeding the last element in a set
160 Do not use the value returned by <tt>end</tt> function to access any item.
161 The returned value can be used only to control reaching the end of the set.
162 For empty set \code begin() == end() \endcode
166 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
169 /// Returns a forward const iterator addressing the first element in a set
171 const_iterator begin() const
175 const_iterator cbegin() const
177 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
181 /// Returns an const iterator that addresses the location succeeding the last element in a set
183 const_iterator end() const
187 const_iterator cend() const
189 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
194 /// Initialize hash set
196 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
197 At construction time you should pass estimated maximum item count and a load factor.
198 The load factor is average size of one bucket - a small number between 1 and 10.
199 The bucket is an ordered single-linked list, the complexity of searching in the bucket is linear <tt>O(nLoadFactor)</tt>.
200 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
203 size_t nMaxItemCount, ///< estimation of max item count in the hash set
204 size_t nLoadFactor ///< load factor: average size of the bucket
205 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
207 // GC and OrderedList::gc must be the same
208 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
210 // atomicity::empty_item_counter is not allowed as a item counter
211 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
212 "atomicity::empty_item_counter is not allowed as a item counter");
214 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
217 /// Clear hash set and destroy it
221 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
226 The function inserts \p val in the set if it does not contain
227 an item with key equal to \p val.
229 Returns \p true if \p val is placed into the set, \p false otherwise.
231 bool insert( value_type& val )
233 bool bRet = bucket( val ).insert( val );
241 This function is intended for derived non-intrusive containers.
243 The function allows to split creating of new item into two part:
244 - create item with key only
245 - insert new item into the set
246 - if inserting is success, calls \p f functor to initialize value-field of \p val.
248 The functor signature is:
250 void func( value_type& val );
252 where \p val is the item inserted.
253 The user-defined functor is called only if the inserting is success.
255 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
256 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
259 template <typename Func>
260 bool insert( value_type& val, Func f )
262 bool bRet = bucket( val ).insert( val, f );
268 /// Updates the element
270 The operation performs inserting or changing data with lock-free manner.
272 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
273 Otherwise, the functor \p func is called with item found.
274 The functor signature is:
277 void operator()( bool bNew, value_type& item, value_type& val );
281 - \p bNew - \p true if the item has been inserted, \p false otherwise
282 - \p item - item of the set
283 - \p val - argument \p val passed into the \p %update() function
284 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
285 refers to the same thing.
287 The functor may change non-key fields of the \p item.
289 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
290 \p second is \p true if new item has been added or \p false if the item with \p key
291 already is in the set.
293 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
294 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
297 template <typename Func>
298 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
300 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
306 template <typename Func>
307 CDS_DEPRECATED("ensure() is deprecated, use update()")
308 std::pair<bool, bool> ensure( value_type& val, Func func )
310 return update( val, func, true );
314 /// Unlinks the item \p val from the set
316 The function searches the item \p val in the set and unlink it from the set
317 if it is found and is equal to \p val.
319 The function returns \p true if success and \p false otherwise.
321 bool unlink( value_type& val )
323 bool bRet = bucket( val ).unlink( val );
329 /// Deletes the item from the set
330 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase
331 The function searches an item with key equal to \p key in the set,
332 unlinks it from the set, and returns \p true.
333 If the item with key equal to \p key is not found the function return \p false.
335 Note the hash functor should accept a parameter of type \p Q that may be not the same as \p value_type.
337 template <typename Q>
338 bool erase( Q const& key )
340 if ( bucket( key ).erase( key )) {
347 /// Deletes the item from the set using \p pred predicate for searching
349 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase "erase(Q const&)"
350 but \p pred is used for key comparing.
351 \p Less functor has the interface like \p std::less.
352 \p pred must imply the same element order as the comparator used for building the set.
354 template <typename Q, typename Less>
355 bool erase_with( Q const& key, Less pred )
357 if ( bucket( key ).erase_with( key, pred )) {
364 /// Deletes the item from the set
365 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase_func
366 The function searches an item with key equal to \p key in the set,
367 call \p f functor with item found, and unlinks it from the set.
368 The \ref disposer specified in \p OrderedList class template parameter is called
369 by garbage collector \p GC asynchronously.
371 The \p Func interface is
374 void operator()( value_type const& item );
378 If the item with key equal to \p key is not found the function return \p false.
380 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
382 template <typename Q, typename Func>
383 bool erase( const Q& key, Func f )
385 if ( bucket( key ).erase( key, f )) {
392 /// Deletes the item from the set using \p pred predicate for searching
394 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase_func "erase(Q const&)"
395 but \p pred is used for key comparing.
396 \p Less functor has the interface like \p std::less.
397 \p pred must imply the same element order as the comparator used for building the set.
399 template <typename Q, typename Less, typename Func>
400 bool erase_with( const Q& key, Less pred, Func f )
402 if ( bucket( key ).erase_with( key, pred, f )) {
409 /// Extracts an item from the set
410 /** \anchor cds_intrusive_MichaelHashSet_rcu_extract
411 The function searches an item with key equal to \p key in the set,
412 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
413 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
415 Depends on \p bucket_type you should or should not lock RCU before calling of this function:
416 - for the set based on \ref cds_intrusive_MichaelList_rcu "MichaelList" RCU should not be locked
417 - for the set based on \ref cds_intrusive_LazyList_rcu "LazyList" RCU should be locked
418 See ordered list implementation for details.
421 #include <cds/urcu/general_buffered.h>
422 #include <cds/intrusive/michael_list_rcu.h>
423 #include <cds/intrusive/michael_set_rcu.h>
425 typedef cds::urcu::gc< general_buffered<> > rcu;
426 typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
427 typedef cds::intrusive::MichaelHashSet< rcu, rcu_michael_list, foo_traits > rcu_michael_set;
429 rcu_michael_set theSet;
432 typename rcu_michael_set::exempt_ptr p;
434 // For MichaelList we should not lock RCU
436 // Now, you can apply extract function
437 // Note that you must not delete the item found inside the RCU lock
438 p = theSet.extract( 10 )
440 // do something with p
444 // We may safely release p here
445 // release() passes the pointer to RCU reclamation cycle:
446 // it invokes RCU retire_ptr function with the disposer you provided for rcu_michael_list.
450 template <typename Q>
451 exempt_ptr extract( Q const& key )
453 exempt_ptr p( bucket( key ).extract( key ) );
459 /// Extracts an item from the set using \p pred predicate for searching
461 The function is an analog of \p extract(Q const&) but \p pred is used for key comparing.
462 \p Less functor has the interface like \p std::less.
463 \p pred must imply the same element order as the comparator used for building the set.
465 template <typename Q, typename Less>
466 exempt_ptr extract_with( Q const& key, Less pred )
468 exempt_ptr p( bucket( key ).extract_with( key, pred ) );
474 /// Checks whether the set contains \p key
476 The function searches the item with key equal to \p key
477 and returns \p true if the key is found, and \p false otherwise.
479 Note the hash functor specified for class \p Traits template parameter
480 should accept a parameter of type \p Q that can be not the same as \p value_type.
482 template <typename Q>
483 bool contains( Q const& key )
485 return bucket( key ).contains( key );
488 template <typename Q>
489 CDS_DEPRECATED("use contains()")
490 bool find( Q const& key )
492 return contains( key );
496 /// Checks whether the set contains \p key using \p pred predicate for searching
498 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
499 \p Less functor has the interface like \p std::less.
500 \p Less must imply the same element order as the comparator used for building the set.
502 template <typename Q, typename Less>
503 bool contains( Q const& key, Less pred )
505 return bucket( key ).contains( key, pred );
508 template <typename Q, typename Less>
509 CDS_DEPRECATED("use contains()")
510 bool find_with( Q const& key, Less pred )
512 return contains( key, pred );
516 /// Find the key \p key
517 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_func
518 The function searches the item with key equal to \p key and calls the functor \p f for item found.
519 The interface of \p Func functor is:
522 void operator()( value_type& item, Q& key );
525 where \p item is the item found, \p key is the <tt>find</tt> function argument.
527 The functor can change non-key fields of \p item.
528 The functor does not serialize simultaneous access to the set \p item. If such access is
529 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
531 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
532 can modify both arguments.
534 Note the hash functor specified for class \p Traits template parameter
535 should accept a parameter of type \p Q that can be not the same as \p value_type.
537 The function returns \p true if \p key is found, \p false otherwise.
539 template <typename Q, typename Func>
540 bool find( Q& key, Func f )
542 return bucket( key ).find( key, f );
545 template <typename Q, typename Func>
546 bool find( Q const& key, Func f )
548 return bucket( key ).find( key, f );
552 /// Finds the key \p key using \p pred predicate for searching
554 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_func "find(Q&, Func)"
555 but \p pred is used for key comparing.
556 \p Less functor has the interface like \p std::less.
557 \p pred must imply the same element order as the comparator used for building the set.
559 template <typename Q, typename Less, typename Func>
560 bool find_with( Q& key, Less pred, Func f )
562 return bucket( key ).find_with( key, pred, f );
565 template <typename Q, typename Less, typename Func>
566 bool find_with( Q const& key, Less pred, Func f )
568 return bucket( key ).find_with( key, pred, f );
572 /// Finds the key \p key and return the item found
573 /** \anchor cds_intrusive_MichaelHashSet_rcu_get
574 The function searches the item with key equal to \p key and returns the pointer to item found.
575 If \p key is not found it returns \p nullptr.
576 Note the type of returned value depends on underlying \p bucket_type.
577 For details, see documentation of ordered list you use.
579 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
581 RCU should be locked before call of this function.
582 Returned item is valid only while RCU is locked:
584 typedef cds::intrusive::MichaelHashSet< your_template_parameters > hash_set;
587 // Result of get() call
588 typename hash_set::raw_ptr ptr;
591 hash_set::rcu_lock lock;
593 ptr = theSet.get( 5 );
598 // Unlock RCU by rcu_lock destructor
599 // ptr can be reclaimed by disposer at any time after RCU has been unlocked
603 template <typename Q>
604 raw_ptr get( Q const& key )
606 return bucket( key ).get( key );
609 /// Finds the key \p key and return the item found
611 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_get "get(Q const&)"
612 but \p pred is used for comparing the keys.
614 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
616 \p pred must imply the same element order as the comparator used for building the set.
618 template <typename Q, typename Less>
619 raw_ptr get_with( Q const& key, Less pred )
621 return bucket( key ).get_with( key, pred );
624 /// Clears the set (non-atomic)
626 The function unlink all items from the set.
627 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
628 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
629 <tt> empty() </tt> may return \p true but the set may contain item(s).
630 Therefore, \p clear may be used only for debugging purposes.
632 For each item the \p disposer is called after unlinking.
636 for ( size_t i = 0; i < bucket_count(); ++i )
637 m_Buckets[i].clear();
638 m_ItemCounter.reset();
642 /// Checks if the set is empty
644 Emptiness is checked by item counting: if item count is zero then the set is empty.
645 Thus, the correct item counting feature is an important part of Michael's set implementation.
652 /// Returns item count in the set
655 return m_ItemCounter;
658 /// Returns the size of hash table
660 Since %MichaelHashSet cannot dynamically extend the hash table size,
661 the value returned is an constant depending on object initialization parameters;
662 see \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for explanation.
664 size_t bucket_count() const
666 return m_nHashBitmask + 1;
671 }} // namespace cds::intrusive
673 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H